Transition Metal Oxides as Electrocatalytic Material in Fuel Cells: A Review

Abstract

Fuel cells make use of electrochemical reactions to produce electricity and majority of the devices have almost no carbon emissions. These devises, and other environmentally friendly energy systems alike, have gained more and more popularity and necessity in the face of high levels of hazardous pollutants accumulated over the years. Electrocatalysts form part of the components of the membrane electrode assembly (MEA) and are a key part in the fuel cell systems. Furthermore, electrocatalysts play a crucial role in supporting electrodes to promote various electrochemical reactions needed to generate energy. Nanostructured transition metal oxides (TMOs) are among the most suitable material candidates for these applications. The interest in TMOs is not new; nanostructured compounds of these materials have good catalytic activity, good durability and high efficiency and have been an interest in catalyst research for years. Studies and developments have reported impressive progress towards these catalyst materials as promising candidates to promote the mass commercialization of fuel cells. Up to now, platinum and platinum group metals have been the ideal choice due to their outstanding properties, however researchers have had to explore other TMs which do not have the let-down of lack of abundance and high cost. Many reviews have been done on the strides made on the invention and developments made over the decades and TMs are no exception to the list. However, platinum, titanium, tungsten, tin and iridium have received more attention and very few papers have been published on the overall oxides of TMs. With the aim of bringing understanding to why TMs contribute greatly towards the improvement studies of catalytic performance, this review discusses recent published studies on progress made to develop TM oxides as electrocatalytic materials in varied applications of fuel cells.